Aqueous Solution Of Boric Acid Research Articles

Effects of Boron Impregnation and Heat Treatment on Some Mechanical Properties of Oak (Quercus petraea Liebl.) Wood

Heat treatment changes some physical, mechanical, and chemical properties of wood. Inorganic borates have been used as wood preservatives for many years. The aim of this study was to investigate the effects of impregnation chemicals on some mechanical properties (bending strength (MOR), modulus of elasticity (MOE), tensile strength parallel to the grain (TS), compression strength parallel to the grain (CS), and shear strength parallel to the grain (SS)) of heat-treated oak (Quercus petraea Liebl.). For this purpose, the oak wood specimens were impregnated with 5% aqueous solution of boric acid (BA) and borax (BX). Then specimens were heat-treated at 160, 190, and 220 °C for 2 and 4 h. According to the results of the study, borax retention value was higher than boric acid. The bending strength, modulus of elasticity in bending, tensile strength parallel to the grain, and shear strength parallel to the grain decreased due to heat treatment. The highest mechanical strength losses were determined in samples heat treated at 220 °C for 4 h. Generally the mechanical strength losses of samples impregnated with borax were lower than non-impregnated controls and specimens impregnated with boric acid.

Effect of Boric Acid Concentration on Viscosity of Slag and Property of Weld Metal Obtained from Underwater Wet Welding

Underwater wet welding is a crucial repair and maintenance technology for nuclear plant. A boric acid environment raises a new challenge for the underwater welding maintenance of nuclear plant. This paper places emphasis on studying the influence of a boric acid environment in nuclear plant on the underwater welding process. Several groups of underwater wet welding experiments have been conducted in boric acid aqueous solution with different concentration (0-35000 ppm). The viscosity of the welding slag and the mechanical properties of welds, such as the hardness, strength, and elongation, have been studied. The results show that with increasing boric acid concentration, the viscosity of the slag decreases first and then increases at a lower temperature (less than 1441 °C). However, when the temperature is above 1480 °C, the differences between the viscosity measurements become less pronounced, and the viscosity tends to a constant value. The hardness and ductility of the joints can be enhanced significantly, and the maximum strength of the weld metal can be reached at 2300 ppm.

Boron isotopic fractionation in aqueous boric acid solutions over synthetic minerals: Effect of layer and surface charge on fractionation factor

Boron isotopic fractionation in boric acid solutions during adsorption on synthetic manganese oxides (birnessite “B” and cryptomelane “C”) and Mg–Al-layered double hydroxide “LDH” was investigated. The materials were characterized by elemental analyses, powder X-ray diffraction, FTIR spectra, BET surface area and zeta potential measurements. Batch experiments were conducted without changing the solution pH to correlate the boron sorption properties of the adsorbents with isotopic fractionation in the associated boric acid solutions. The results showed that boron isotopic composition of the contact solution is heavily dependent on the selective adsorption of B(OH)3 or B(OH)4− species due to the charge properties of the minerals. With B and C, possessing negatively charged surfaces, 10B(OH)4− was preferentially fractionated in the solution due to the transfer of the Lewis acidic 11B(OH)3 species while with LDH selective adsoption of 10B(OH)4− by positive layers was favorable resulting in the enrichment of the heavier isotope in the solution.

Correlation between Preparation Condition and Performance of Pt/SnO2/KB for Cathode Catalyst of PEMFC

Proton exchange membrane fuel cells (PEMFCs) are promised as the power sources for stationary and automobile application. However, further improvement of the durability of cathode catalyst is required for full-scale commercialization.It is recognized that Pt/C catalyst is degraded by electrochemical Ostwald ripening and migration of Pt particles at the cathode [1]. And also, carbon corrosion is serious under increasing the cathode potential. Considering the degradation mechanisms, we reported that surface modification of carbon support with high durable material as tin dioxide is promising technique [2]. In this study, correlation between preparation condition and performance of Pt/SnO2/KB is investigated. For preparation of Pt/SnO2/KB, Ketjen black modified with tin oxide particles (SnO2/KB) is firstly prepared and then Pt was loaded on SnO2/KB.SnO2/KB was prepared by our recipe as reported elsewhere [2, 3]. Ketjen Black EC-300j (abbr. as KB, Ketjen Black International Co. Ltd) was dispersed in Tin fluoride solution for 24 h. Then, it was dispersed in boric acid aqueous solution and finally was heated at various temperatures under Ar atmosphere.Loading of Pt particles was carried out by the impregnation method [2]. Then, they were heated at various temperatures under N2atmosphere. The prepared catalysts were characterized by TG, SEM, ICP and CO absorption pulse test. In particular, Pt particle size was estimated by CO absorption pulse test.Pt/SnO2/KB, Nafion® solution (Aldrich) and i-propanol was mixed ultrasonically to prepare the catalyst ink. The ink was dropped on a glassy carbon disk and was used for the working electrode to measure the catalytic activity for ORR and the durability. An electrochemical cell filled with 0.1 mol dm-3 HClO4 aqueous solution was used. ORR activity was measured under O2atmosphere by a rotating disk electrode technique.The potential pulse durability tests were conducted between 1.0 V and 0.6 V to evaluate Pt durability. Electrochemical active surface area (ECA) of Pt catalysts was estimated after an arbitrary period by cyclic voltammetry (CV) during the durability test. Figure 1 shows SEM image of Pt/SnO2/KB heated at 120oC and 300oC. SnO2 particles of ca. 10 nm in the diameter were observed on KB surface. The Pt particle size of Pt/SnO2/KB heated at 120oC is estimated as ca. 2.3 nm; on the other hand, that of Pt/SnO2/KB was ca. 1.6 nm after heating at 300oC.Table 1 shows specific and mass activity for ORR of Pt/SnO2/KB heated at 120oC and 300oC. ORR activity of both catalysts is approximately same. We reported that ORR activity is increased by SnO2/KB when SnO2 weight ratio is over 35wt% [3]. Unfortunately, ORR activity is almost same for the catalyst without SnO2 in this study, which may be caused by aggregation of SnO2particles.Figure 2 shows Pt durability test results. The ECA remaining rates for both of these catalysts are approximately same. The detail results including the effect of weight ratio of SnO2, heat treatment temperature before and after Pt loading on the activity as well as the durability will be also report.

Evaluation of oriented amorphous regions in polymer films during uniaxial deformation; structural characterization of a poly(vinyl alcohol) film during stretching in boric acid aqueous solutions

We have improved the conventional analytical method of the scattering data obtained with in-situ synchrotron X-ray scattering experiments, which is applicable to the structural characterization of the film during stretching. Four components of molecular chains in the film are divided from two-dimensional wide-angle X-ray diffraction patterns. These components are the oriented crystals, the unoriented ones, the oriented amorphous chains, and the unoriented ones, respectively. This method allows to evaluate directly the degree of orientation of the amorphous chains and the amount of the oriented amorphous fraction in addition to each evaluation for the crystalline regions. This method is applied to the structural characterization of the poly(vinyl alcohol) (PVA) film during stretching in boric acid aqueous solutions, suggesting that boric acid accelerates orientation of molecular chains in the amorphous regions, and increases the oriented amorphous fraction by producing the cross-links between the PVA chains and hindering strain-induced crystallization. At a film break on stretching in the 3 wt% boric acid solution, the oriented amorphous fraction increases up to 70%, which is much higher compared to that in the film stretched in water, 45%. POLYM. ENG. SCI., 55:513–522, 2015. © 2014 Society of Plastics Engineers

Pool Boiling Heat Transfer of Borated (H3BO3) Water on a Nanoporous Surface

With regard to potential application in pressurized water reactors (PWRs), a nanoporous heated surface was tested in pool boiling of an aqueous solution of boric acid (H3BO3), or borated water (1% volume concentration). The effect of system pressure and surface orientation on pool boiling heat transfer (BHT) was studied. The nanoporous surface consisted of a coating of alumina nanoparticles applied on a 1 cm2 flat copper surface through nanofluid boiling. An uncoated surface in borated water was similarly tested, and due to boric acid deposition, the BHT degraded and the critical heat flux (CHF) enhanced relative to pure water. Also, the possibility of transient pool boiling behavior of borated water was investigated but none was detected. With pressure and orientation variation, the nanoporous surface imposed on borated water showed a trend of further CHF enhancement to the CHF limit produced by the nanoporous surface in pure water. Over the nanoporous surface, the CHF of borated water was increasingly better with decreasing pressure, than that over the plain surface. However, BHT degraded slightly further. Boric acid deposition over the nanoporous surface was believed to be the source of this BHT degradation, but played no apparent role in the further CHF enhancement.

Electrical characterization of liquid-phase-deposited SiON on (NH4 )2 S-treated GaAs

The electrical characteristics of liquid-phase-deposited (LPD) silicon oxynitride film on ammonium-sulfide-treated p-type (100) gallium arsenide (GaAs) substrate were investigated. Hydrofluosilicic acid, ammonia, and boric acid aqueous solutions were used as precursors. The electrical characteristics of silicon oxynitride film are a function of the boric acid volume in the growth solution and much improved on GaAs substrate with ammonium-sulfide treatment. The leakage currents can reach 1.24 × 10−7 and 7.85 × 10−7 A cm−2 at ±0.5 MV cm−1. The lowest interface state density and the dielectric constant are 3.32 × 1011 cm−2 eV−1 and 4.74, respectively.

Preparation of zinc borates with different structures and morphologies and their effect on thermal and oxidative stability of polyvinyl alcohol

Abstract Zinc borates with different structures and morphologies were selectively prepared starting from zinc sulfate hydroxide (Zn 4 SO 4 (OH) 6 ) and boric acid in aqueous solution. When the reaction temperatures were 80 and 90 °C, platelet-like and polyhedral zinc borates with the formula of 2ZnO·3B 2 O 3 ·3H 2 O were formed, respectively. When the reaction temperature was less than 80 °C, rod-like heptahydrate zinc borates with the formula of 2ZnO·3B 2 O 3 ·7H 2 O were formed. The morphology of zinc borates (2ZnO·3B 2 O 3 ·3H 2 O) changed from platelet to polyhedron at the reaction temperature of 90 °C with increasing the water content in the reaction solution. The presence of polyethylene glycol and sodium dodecyl benzene sulfonate in the reaction solution favored the formation of small-sized polyhedral 2ZnO∙3B 2 O 3 ∙3H 2 O particles. The presence of citric acid favored the formation of 2ZnO∙3B 2 O 3 ∙3H 2 O platelets. The chemical structure and morphology of the zinc borates significantly affected their performances on improving the thermal and oxidative stability of polyvinyl alcohol.

Effect of the Addition of Boric Acid to Zirconia Synthesized Employing Pore-forming Agents

The preparation and characterization of borated zirconia calcined at 320°C was studied. The zirconia was prepared using zirconyl chloride as precursor and ammonium hydroxide as precipitating agent. Pore-forming agents during zirconia synthesis were added, specifically glucose or polyethylene glycol (PEG) of different molecular weight. After drying, an aqueous solution of boric acid was added to the zirconia. Zirconias without the addition of boric acid were also prepared. The specific surface area of the borated zirconias is higher than those of the samples without boron. The addition of PEG led to a mean pore size larger than 3nm, while with glucose the value was somewhat lower, indicating that PEGs are more effective pore-forming agents. By X-ray diffraction, it was observed that the materials have amorphous characteristics. The FT-IR spectra showed that the washing of the samples seems to be effective in the removal of the pore-forming agents, and the bands assigned to boron species are present in the borated zirconias. On the other hand, it was estimated that all the borated zirconias presented very strong acid sites. So, solids with adequate characteristics to be used as catalysts in acid reactions were synthesized.

Comparison of electrical and optical properties of Al/SiO 2 /n-GaN and ITO/SiO 2 /n-GaN metal–oxide–semiconductor photodetectors

Gallium nitride (GaN) MOS ultraviolet photodetector was fabricated using silicon dioxide (SiO2) insulator grown by a low temperature (30–40°C) and reliable method of liquid-phase deposition (LPD). The LPD process uses a supersaturated acid aqueous solution of hydrofluosilicic (H2SiF6) as a source liquid and an aqueous solution of boric acid (H3BO3) as a deposition rate controller. In this study, the LPD SiO2 was prepared at 40°C with concentrations of H2SiF6 and H3BO3 at 0.4 and 0.01 M, respectively. The authors have prepared Al gate/10 nm LPD-SiO2/n-GaN (sample A) and indium tin oxide (ITO) gate/10 nm LPD-SiO2/n-GaN (sample B). The dark current density was as low as 3.66×10−8 A/cm2 with an applied field of 5 MV/cm for sample B. For an incident light wavelength of 366 nm with an intensity of 4.15 mW/cm2 and a −10 V reverse bias, it was found that the measured responsivity was around 0.145 and 0.292 A/W for samples A and B, respectively. The photocurrent-to-dark current contrast ratio is up to 104 by using an ITO gate of the metal–oxide–semiconductor PD with an incident light wavelength of 366 nm. Defect-assisted tunnelling was invoked to explain these results.

Photodetective characteristics of Al/LPD-oxide/n-type Si MOS with tunnelling structures

The aluminum/oxide/n-type Si MOS tunnelling structure is utilised as a photodetector. The silicon dioxide (SiO2) insulator was grown by a low temperature (30–40°C) and reliable method of liquid-phase deposition (LPD). The LPD process uses a supersaturated acid aqueous solution of hydrofluosilicic (H2SiF6) as a source liquid and an aqueous solution of boric acid (H3BO3) as a deposition rate controller. In this Letter, the LPD SiO2 was prepared at 40°C with concentrations of H2SiF6 and H3BO3 at 0.4 and 0.01 M, respectively. Field-emission scanning electron microscopy shows the LPD–SiO2 with grain size ranging 40–50 nm. The element analysis of LPD–SiO2, deposited onto n-type Si, is investigated by using Fourier transform infrared spectroscopy. The on/off ratio calculated from the dark and photo current densities rapidly changes at the threshold optical-power density. Defect-assisted tunnelling was invoked to explain these results. The authors suggest that a suitable LPD technology for the fabrication of the MOS tunnelling diode can be achieved.

EFFECT OF SOLUBLE ADDITIVES, BORIC ACID (H3BO3) AND SALT (NaCl), IN POOL BOILING HEAT TRANSFER

The effects on pool boiling heat transfer of aqueous solutions of boric acid (H₃BO₃) and sodium chloride (NaCl) as working fluids have been studied. Borated and NaCl water were prepared by dissolving 0.5~5% volume concentration of boric acid and NaCl in distilled-deionized water. The pool boiling tests were conducted using 1 x 1 ㎠ flat heaters at 1 atm. The critical heat flux (CHF) dramatically increased compared to boiling pure water. At the end of boiling tests it was observed that particles of boric acid and NaCl had deposited and formed a coating on the heater surface. The CHF enhancement and surface modification during boiling tests were very similar to those obtained from boiling with nanofluids. Additional experiments were carried out to investigate the reliability of the additives deposition in pure water. The boric acid and NaCl coatings disappeared after repeated boiling tests on the same surface due to the soluble nature of the coatings, thus CHF enhancement no longer existed. These results demonstrate that not only insoluble nanoparticles but also soluble salts can be deposited during boiling process and the deposited layer is solely responsible for significant CHF enhancement.

Synthesis and structure of [C 6N 4H 20] 0.5[B 5O 6(OH) 4]: A new organically templated pentaborate with white-light-emission

A new organically templated pentaborate [C 6N 4H 20] 0.5[B 5O 6(OH) 4] ( 1a) was prepared by reactions of triethylenetetramine (TETA) with excess boric acid in aqueous solution and characterized by elemental analysis, FTIR, TG-DTA, powder X-ray diffraction and photoluminescence spectroscopy. The structure of 1a was determined by a single-crystal X-ray diffraction. It crystallizes in the monoclinic system with space group P2(1)/ c, a=9200(3) Å, b=14.121(5) Å, c=10.330(4) Å, β=91.512(4)°, V=1341.4(9) Å 3, and Z=4. The luminescent properties of the compound were studied, and a green–blue luminescence occurs with an emission maximum at 507 nm upon excitation at 430 nm. The photoluminescence of 1a can be modified from green–blue to white by means of a simple heat-treatment process. The white-light-emission of sample 1c makes the pentaborate a good candidate for display and lighting applications in the white LED.

Leaching of boron from wood impregnated with preservative solutions based on boric acid and liquefied wood

Reducing boron leaching from impregnated wood has been one of the most challenging tasks for at least 50 years. In order to slow down the leaching of boron, aqueous solutions of boric acid were combined with liquefied spruce wood. The results clearly showed that leaching of boron from spruce wood impregnated with preservative solutions based on boric acid and liquefied wood was significantly reduced.

Preparation and properties of the barium borate glassy matrix composite materials containing fused silica and monoclinic zirconia

In this work, the LTCC composite materials containing fused silica and monoclinic zirconia ceramic particles, respectively, which based on the composite matrix composed of the barium borate glassy matrix and α-alumina ceramic particles, were prepared by traditional solid-state preparation process at a sintering temperature of 900 °C. Sintering mechanism and physical properties, e.g. dielectric properties and coefficient of thermal expansion (CTE), of the LTCC composite ceramics are investigated and discussed in detail in terms of their mineral phase composition. The results indicate that a barium borate glassy phase can be easily formed from a barium borate compound, which is obtained by the chemical combination of barium hydroxide octahydrate and an aqueous solution of boric acid, at a sintering temperature of 900 °C. In turn, the barium borate glassy melts can supply a liquid phase sintering aid for the fabrication of the LTCC composite ceramics with the sintering temperature of 900 °C during sintering. The introduction of the α-alumina ceramic particles to the barium borate glassy matrix can improve the sintering behavior whereas the presence of fused silica or monoclinic zirconia particles in the composite ceramics is important to adjust the dielectric, thermal and mechanical properties of the LTCC composite materials. The work may be referenced for the fabrication of multi-layer LTCC structures with tailored physical properties.

Sorption properties of wood impregnated with aqueous solution of boric acid and montan wax emulsion

AbstractNonbiocidal techniques for wood protection have become more and more important in the last few years. One of the possible treatments to enhance wood durability is use of water repellents. In this research, the influence of one of the possible water repellents, the montan wax emulsion, on the moisturizing and the sorption characteristics of impregnated wood was investigated. To achieve a better protection against wood decay fungi, wood was impregnated with montan wax emulsion enriched with boric acid. The equilibrium moisture content (MC) was monitored during the adsorption and the desorption processes at five levels of relative air humidity (RH1 = 20%, RH2 = 33%, RH3 = 65%, RH4 = 88%, and RH5 = 98%). Water repellence efficiency was monitored in the chamber with high RH (87%) and during dipping in the water. Impregnated samples were also exposed outdoors in a covered position for 5 months to determine MC changes according to changes in outdoor humidity and temperature. The results showed that the sorption properties of the impregnated wood are strongly related to retention of preservative solutions after impregnation and its composition. Montan wax reduced equilibrium MC of the impregnated wood up to 25% (relatively), whereas specimens impregnated with combination of montan wax and boric acid resulted in decreased MC in some cases and in increased MC in some cases. The Guggenheim–Andersen–deBoer model of sorption isotherms was fitted to experimental data to explain the sorption mechanisms. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Polarizer effect and structure of iodinated before and after casting poly(vinyl alcohol) film

AbstractPoly(vinyl alcohol) (PVA)/iodine polarizing film was manufactured as follows: PVA iodinated in solution before casting (IBC film) and iodinated again after casting (IBC + IAC film) and then the IBC + IAC film was drawn in boric acid aqueous solution (IBC + IAC polarizing film), to improve the durability of the polarizing film under a humid and warm atmosphere. These effects were examined by investigating the structural and optical properties of the IBC, IBC + IAC, and IBC + IAC polarizing films. In the IBC state, the PVA chain segments that combined boric acid and iodine were regarded as defects of the crystal, the formation of I3− decreased with respect to weight gain of boric acid. In the IBC + IAC state, the strength of the peak corresponding to I3− decreased and the I5− peak increased. The iodine ions penetrated into crystal of the IBC state during the IAC process and formed a new PVA/iodine complex crystal at the 2θ = 20° in the X‐ray diffraction curves. In the IBC + IAC polarizing film state, another type of polarizing film (IBC + IAC polarizing film‐H) containing I3− ions mainly was manufactured as well as the IBC + IAC polarizing film to compare the effects of the I3− and I5− ions on the durability of the polarizing films. The durability of the I3− ions that were complexed with the PVA chain was higher than the I5− ions, which could possibly be separated to I3− and I2. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Role of boric acid for a poly (vinyl alcohol) film as a cross-linking agent: Melting behaviors of the films with boric acid

We have investigated the role of boric acid as a cross-linking agent for a poly (vinyl alcohol) (PVA) film when the film is immersed in boric acid aqueous solution. DSC results show that the films with boric acid exhibit the higher glass transition temperatures than that of the PVA film without boric acid, when the films are dried after immersing in boric acid aqueous solutions with various boric acid concentrations, implying that boric acid penetrating into the films slows down the PVA molecular motion. Furthermore, simultaneous small-angle X-ray scattering and wide-angle X-ray diffraction measurements were performed on the melting processes of the PVA films with boric acid. We found that the crystallite size increase originated from melting and recrystallization do not occur for the PVA films with boric acid, whereas in the case of the PVA without boric acid the crystallite size is enlarged in both directions parallel and perpendicular to the chain axis via melting and recrystallization on melting. These indicate that chemical reactions of boric acid to the PVA molecular chains in amorphous regions resulted in cross-linking points take place in boric acid aqueous solutions, inhibiting recrystallization on melting, because the cross-links slow down the PVA molecular motion and must not be included in the crystalline domains.

Preparation of the LTCC composite ceramics with low permittivity

In this work, the LTCC composite ceramics containing α-alumina and quartz based on the binary system BaO–B2O3 were prepared by traditional solid-state preparation process at a sintering temperature of 900 °C. Sintering mechanism and physical properties of the LTCC composite ceramics are investigated and discussed in detail in terms of their mineral phase composition. The results indicate that, by the chemical combination of barium hydroxide octahydrate and an aqueous solution of boric acid, a barium borate phase can be formed form the binary system BaO–B2O3 and consequently supply a liquid sintering aid for the fabrication of LTCC composite ceramics at a sintering temperature of 900 °C. The introduction of α-alumina to the binary system BaO–B2O3 can improve the sintering behavior whereas the presence of quartz in the composite ceramics is important to achieve low permittivity. By the combination of α-alumina, quartz and BaO–B2O3 composition, the dense LTCC composite ceramics, which is characterized by excellent dielectric properties (permittivity: 3.56; 4.83; dielectric loss: 3 × 10−4; 4 × 10−4), can be fabricated availably.

Effect of boric acid treatment on the crystallinity and drawability of poly(vinyl alcohol)–iodine complex films

A film iodinated at solution state before casting (BIBC film) and a film iodinated after casting (BIAC film) were prepared by casting an aqueous solution of poly(vinyl alcohol) (PVA) including I2/KI and boric acid, and by successively soaking the PVA film in aqueous solutions of boric acid and I2/KI, respectively. The boric acid-induced and I2/KI-induced weight gains relative to the PVA were 3, 5, 7, and 10%, and 3, 5, 10, and 20%, respectively. The effects of boric acid and iodine on the crystallinity and drawability of the films were investigated. Although the crystalline structure of the BIAC films was not affected by boric acid, the boric acids in the PVA solution containing I2/KI may have formed intra-molecular cross-links on the PVA chain to accelerate the formation of the PVA–iodine complex evenly, and subsequently interrupt the PVA crystallization through the BIBC film formation to render the resultant film slightly crystalline or practically amorphous. This occurred even at a much lower I2/KI-induced weight gain (20%) than the minimum weight gain (125%) at which the iodinated at solution state before casting film without boric acid indicated a practically amorphous state. The maximum draw ratio of the films generally decreased with increasing boric acid content, which was mainly attributed to the increase of the extended segments of the PVA chains in the amorphous region due to the cross-links formed with the boric acids. The maximum draw ratios of the BIBC films tended to decrease more severely than those of the BIAC films.